1. Technical Field
This device relates to automated digging machines that have been developed to engage, cut and remove manholes found in street environments. Such machines typically cut the interior casing of the manhole in preparation for removal, repair and replacement due to changes in street elevations associated with resurfacing or repair and replacement.
2. Description of Prior Art
Prior art devices of this type have relied on a variety of cutting and removal devices, see for example U.S. Pat. Nos. 4,924,951, 4,968,101, 5,470,131, 6,536,987, 6,709,064 and 6,755,481.
U.S. Pat. No. 4,924,951 claims a manhole cutter for cutting a fixed diameter circular groove of a fixed depth around the surface of a manhole. The cutter is of a continuous ring design with spaced sections having cutting teeth elements.
A vertical asphalt and concrete milling device is illustrated in U.S. Pat. No. 4,968,101 having a large circular cutting drum with continuous teeth along the bottom edge.
In U.S. Pat. No. 5,470,131 a method and apparatus for cutting circular slots in pavements extending about a manhole casing is disclosed in which a self-propelled core cutting device has an open drum shaped cutting blade which is rotated by a hydraulic drive means to engage and cut the surface about an existing manhole.
U.S. Pat. No. 6,536,987 discloses a quick manhole/manhole construction method and related device in which a cutting unit is positioned within the manhole and the cuts using a circular saw for removal thereof.
U.S. Pat. No. 6,709,064 is directed towards a method and device for detaching or cutting an embedded manhole frame that positions a circular cutting saw blade within the manhole so as to cut from the inside the existing hole casing for removal.
U.S. Pat. No. 6,755,481 claims a method for cutting asphalt or concrete around a manhole using a circular offset cutting blade.